Method for manufacturing superelastic beta titanium articles and the articles derived therefrom

ABSTRACT

An article is manufactured from a composition comprising about 8 to about 10 wt % molybdenum, about 2.8 to about 6 wt % aluminum, up to about 2 wt % chromium, up to about 2 wt % vanadium, up to about 4 wt % niobium, with the balance being titanium, wherein the weight percents are based on the total weight of the alloy composition. An article is manufactured by a method comprising forming a shape from a composition comprising about 8 to about 10 wt % molybdenum, about 2.8 to about 6 wt % aluminum, up to about 2 wt % chromium, up to about 2 wt % vanadium, up to about 4 wt % niobium, with the balance being titanium, wherein the weight percents are based on the total weight of the alloy composition; cold working the shape; and heat treating the shape.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. application Ser. No.10/609,004 filed on Jun. 27, 2003 and to U.S. Provisional Application60/392,620 filed Jun. 27, 2002, the entire contents of which areincorporated herein by reference.

BACKGROUND

[0002] This disclosure relates to superelastic β titanium alloys,methods for manufacturing these alloys and articles derived therefrom.

[0003] Alloys that undergo a martensitic transformation may exhibit a“shape memory effect”. As a result of this transformation, the hightemperature phase known as “austenite” changes its crystalline structurethrough a diffusion-less shear process adopting a less symmetricalstructure called ‘martensite’. This process may be reversible as inshape memory alloys and therefore upon heating, the reversetransformation occurs. The starting temperature of the cooling ormartensitic transformation is generally referred to as the M_(s)temperature and the finishing temperature is referred to as the M_(f)temperature. The starting and finishing temperatures of the reverse oraustenitic transformation are referred to as A_(s) and A_(f)respectively.

[0004] At temperatures below the A_(f), alloys undergoing a reversiblemartensitic phase transformation may be deformed in their hightemperature austenitic phase through a stress-induced martensitictransformation as well as in their low temperature martensitic phase.These alloys generally recover their original shapes upon heating abovethe A_(f) temperature and are therefore called “shape memory alloys”. Attemperatures above the A_(f), the stress-induced martensite is notstable and will revert back to austenite upon the release ofdeformation. The strain recovery associated with the reversion ofstress-induced martensite back to austenite is generally referred to as“pseudoelasticity” or “superelasticity” as defined in ASTM F2005,Standard Terminology for Nickel-Titanium Shape Memory Alloys. The twoterms are used interchangeably to describe the ability of shape memoryalloys to elastically recover large deformations without a significantamount of plasticity due to the mechanically induced crystalline phasechange.

[0005] Nitinol is a shape memory alloy comprising a near-stoichiometricamount of nickel and titanium. When deforming pseudoelastic nitinol, theformation of stress-induced-martensite allows the strain of the alloy toincrease at a relatively constant stress. Upon unloading, the reversionof the martensite back to austenite occurs at a constant, but different,stress. A typical stress-strain curve of pseudoelastic nitinol thereforeexhibits both loading and unloading stress plateaus. However, since thestresses are different, these plateaus are not identical, which isindicative of the development of mechanical hysteresis in the nitinol.Deformations of about 8 to about 10% can thus be recovered in thepseudoelastic nitinol. Cold worked Nitinol also exhibits extended linearelasticity. Nitinol compositions, which display linear elasticity do notdisplay any plateau but can recover a strain of up to 3.5%. Thisbehavior is generally termed “Linear Superelasticity” to differentiatefrom transformation induced “Pseudoelasticity” or “Superelasticity”.These properties generally make nitinol a widely used material in anumber of applications, such as medical stents, guide wires, surgicaldevices, orthodontic appliances, cellular phone antenna wires as well asframes and other components for eye wear. However, nitinol is difficultto fabricate by forming and/or welding, which makes the manufacturing ofarticles from it expensive and time-consuming. Additionally, users ofnickel containing products are sometimes allergic to nickel.

SUMMARY

[0006] In one embodiment, an article is manufactured from a compositioncomprising about 8 to about 10 wt % molybdenum, about 2.8 to about 6 wt% aluminum, up to about 2 wt % chromium, up to about 2 wt % vanadium, upto about 4 wt % niobium, with the balance being titanium, wherein theweight percents are based on the total weight of the alloy composition.

[0007] In another embodiment, an article manufactured from a compositioncomprises about 8.9 wt % molybdenum, about 3.03 wt % aluminum, about1.95 wt % vanadium, about 3.86 wt % niobium, with the balance beingtitanium.

[0008] In yet another embodiment, an article manufactured from acomposition comprises about 9.34 wt % molybdenum, about 3.01 wt %aluminum, about 1.95 wt % vanadium, about 3.79 wt % niobium, with thebalance being titanium.

[0009] In yet another embodiment, an article is manufactured by a methodcomprising forming a shape from a composition comprising about 8 toabout 10 wt % molybdenum, about 2.8 to about 6 wt % aluminum, up toabout 2 wt % chromium, up to about 2 wt % vanadium, up to about 4 wt %niobium, with the balance being titanium, wherein the weight percentsare based on the total weight of the alloy composition; cold working theshape; and heat treating the shape.

[0010] In yet another embodiment, an article is manufactured by a methodcomprising swaging a wire having a composition comprising about 8 toabout 10 wt % molybdenum, about 2.8 to about 6 wt % aluminum, up toabout 2 wt % chromium, up to about 2 wt % vanadium, up to about 4 wt %niobium, with the balance being titanium, wherein the weight percentsare based on the total weight of the alloy composition; cold working theshape; and heat treating the shape.

[0011] In yet another embodiment, the article manufactured from a βtitanium alloy may be an eyewear frame and components, face inserts andgolf club heads, orthodontic arch wires, dental implants, medicalstents, filters, baskets, surgical instruments, orthopedic prostheses,orthopedic fracture fixation devices, spinal fusion and scoliosiscorrection devices or a catheter introducer (guide wire) and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 represents an isometric view of the eyewear frame 100;

[0013]FIG. 2 represents a schematic of one possible construction of thetemple 130;

[0014]FIG. 3A is a front, side and bottom view of a beveled edge insertfor a golf club;

[0015]FIG. 3B is a bottom view of a tongue and groove edge insert for agolf club;

[0016]FIG. 4A is a front view of a club face with an insert;

[0017]FIG. 4B is a bottom view of FIG. 4A showing the cut-out profilefor the insert;

[0018]FIG. 5 is a front view of a golf club face with an insert;

[0019]FIG. 6A-D is a schematic representation of one method ofassembling the golf club;

[0020]FIG. 7 is a graphical representation showing the effect ofmolybdenum content on elastic recovery;

[0021]FIG. 8 is a graphical representation of the effect of aging at350° C. on the elastic recovery of Sample 4 from Table 1;

[0022]FIG. 9 is a graphical representation of the effect of aging at350° C. on the elastic recovery of Sample 5 from Table 1;

[0023]FIG. 10 is a graphical representation showing the effect of agingat 350° C. on the elastic recovery of Sample 6 from Table 1;

[0024]FIG. 11 is a graphic representation showing the effect of aging atabout 250 to about 550° C. for 10 seconds on the elastic recovery ofSample 4 from Table 1;

[0025]FIG. 12 is a graphic representation showing the effect of aging atabout 250 to about 550° C. for 10 seconds on the elastic recovery ofSample 5 from Table 1;

[0026]FIG. 13 is a graphical representation showing the effect ofcumulative cold drawing reduction on the UTS of Sample 11 from Table 2;

[0027]FIG. 14 is a graphical representation showing the effect ofcumulative cold drawing reduction on the Young's Modulus of Sample 11from Table 2;

[0028]FIG. 15 is a graphical representation showing the effect oftensile stress-strain curve for a wire having the composition of Sample11 from Table 2 with 19.4% drawing reduction, tested to 2% strain;

[0029]FIG. 16 is a graphical representation showing the effect oftensile stress-strain curve for a wire having the composition of Sample11 from Table 2 with 19.4% drawing reduction, tested to 4% strain;

[0030]FIG. 17 is an optical micrograph showing the microstructure of acold drawn wire having the composition of Sample 10 from Table 2 with a14% reduction;

[0031]FIG. 18 is an optical micrograph showing partially recrystallizedmicrostructure of a cold-drawn wire having the composition of Sample 10from Table 2 having a 14% reduction after heat-treating at 816° C. for30 minutes;

[0032]FIG. 19 is an optical micrograph showing fully recrystallizedmicrostructure of a cold-drawn wire having the composition of Sample 10from Table 2 having a 14% reduction after heat-treating at 871° C. for30 minutes;

[0033]FIG. 20 is an optical micrograph showing the microstructure of abetatized Sample 10 from Table 2 after aging at 816° C. for 30 minutes;

[0034]FIG. 21 is an optical micrograph showing the microstructure of abetatized Sample 10 from Table 2 after aging at 788° C. for 30 minutes;

[0035]FIG. 22 is a graphical representation showing the UTS of betatizedSample 10 from Table 2 after aging at 500-900° C. for 30 minutes;

[0036]FIG. 23 is a graphical representation showing the ductility ofbetatized Sample 10 from Table 2 after aging at 500-900° C. for 30minutes;

[0037]FIG. 24 is a graphical representation showing a tensilestress-strain curve tested to 4% tensile strain of a wire having thecomposition of Sample 11 from Table 2 after strand annealing at 871° C.;and

[0038]FIG. 25 is an optical micrograph showing the microstructure of awire having the composition of Sample 11 from Table 2 after strandannealing at 871° C.

[0039]FIG. 26 is a schematic of a stent;

[0040]FIG. 27 represents a schematic of a perspective view of a catheterand needle assembly;

[0041]FIG. 28 represents an exploded schematic of a perspective view ofthe catheter assembly and needle assembly including the needle tipprotector;

[0042]FIG. 29 is a partially exploded view of the bone reduction andfixation device showing a driver and cannulated, internally andexternally threaded bone screw;

[0043]FIG. 30 is a side elevational view of the bone reduction andfixation assembly of FIG. 29;

[0044]FIG. 31 is a cross-sectional view of the bone reduction andfixation assembly of FIG. 30;

[0045]FIG. 32 depicts the plan of one configuration of an arch wire;

[0046]FIG. 33 depicts an enlarged side view on line 2-2 of FIG. 32; and

[0047]FIG. 34 depicts a plan of an arch wire with lingually positionedorthodontic brackets;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0048] Disclosed herein are articles manufactured from β titanium alloyssuch as eyewear frames and frame components, face inserts and heads forgolf clubs, orthodontic arch wires, dental implants, orthopedicprostheses, orthopedic fracture fixation devices, spinal fusion andscoliosis correction instruments, medical stents, filters, baskets, acatheter introducer (guide wire) and the like. The β titanium alloyexhibits pseudo-elasticity as well as linear superelasticity and mayadvantageously be welded, brazed, or soldered to other metals or alloys.The articles manufactured from the β titanium alloy can also be deformedinto various shapes at ambient temperature and generally retain the highspring back characteristics associated with superelasticity. It is to benoted that all ranges disclosed herein are inclusive and combinable.

[0049] Pure titanium has an isomorphous transformation temperature at882° C. The body centered cubic (bcc) structure, which is calledβ-titanium, is stable above the isomorphous transformation temperatureand the hexagonal close packed (hcp) structure, which is called αtitanium is generally stable below this temperature. When titanium isalloyed with elements such as vanadium, molybdenum, and/or niobium, theresulting alloys have an increased β phase stability at temperaturesless than or equal to about 882° C. (β transus temperature). On theother hand, when alloyed with elements such as aluminum or oxygen, thetemperature range of the stable α phase is increased above theisomorphous transformation temperature. Elements which have the effectof increasing the β phase temperature range are called the βstabilizers, while those capable of extending the α phase temperaturerange are called the a stabilizers.

[0050] Unalloyed titanium transforms allotropically frombody-center-cubic (bcc) β phase to hexagonal-close-packed (hcp) α phaseupon cooling through the β transus temperature of 882° C. Depending onthe alloying composition and thermo-mechanical processing, the ultimatemicrostructure of titanium alloys may have α, α+β, or β phases. Theso-called β alloys contain critical amounts of β-stabilizing elementsand exhibit extended β stability at high temperatures and a reduction inβ transus temperature to lower temperatures as elemental concentrationincreases. When a certain concentration level is achieved, the β phasecan be retained upon rapid cooling from the beta phase field, althoughit is metastable. The metastable β titanium alloys may undergo latticetransformations such as martensitic transformation under applied stress.Hence, titanium alloys at critical range of β stability may exhibitshape memory effect and superelasticity. The β-stabilizing elements arefurther classified into β-isomorphous group and β-eutectoid group.β-isomorphous elements such as V, Zr, Hf, Nb, Ta, Mo and Re stabilizethe β phase by forming a simple α→α transformation while β-eutectoidelements such as Cr, Mn, Fe, Co, Ni, Cu, Pd, Ag, W, Pt and Au stabilizethe β phase by forming β→α+γ transformations.

[0051] The stability of the β phase can be expressed as the sum of theweighted averages of the elements that comprise the alloy, often knownas the molybdenum equivalent (MO_(eq.)). P. Bania, Beta Titanium Alloysin the 1990's, TMS, Warrendale, 1993, defines the MO_(eq.) in thefollowing equation (1) as

MO_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W−1.00Al  (1)

[0052] wherein Mo is molybdenum, Nb is niobium, Ta is tantalum, V isvanadium, Co is cobalt, Cr is chromium, Cu is copper, Fe is iron, Mn ismanganese, Ni is nickel, W is tungsten and Al is aluminum and whereinthe respective chemical symbols represent the amounts of the respectiveelements in weight percent based on the total weight of the alloy. Inone embodiment, the aluminum can be substituted by carbon, boron,germanium and/or gallium.

[0053] Hf (hafnium), Sn (tin) and Zr (zirconium) exhibit similarly weakeffects on the β stability. Although they act to lower the β transus,these elements are considered neutral additions. US Air Force TechnicalReport AFML-TR-75-41 has suggested that Zr has a small Mo equivalent of0.25 while Al is an α stabilizer having a reverse effect to that of Mo.Hence, the Mo equivalent in weight percent is calculated according tothe following equation (2) which is a modified form of the equation (1):

MO_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W+0.25(Sn+Zr+Hf)−1.00Al  (2)

[0054] In general it is desirable to have a shape memory alloy thatdisplays superelasticity and/or pseudoelasticity, which has a molybdenumequivalent of about 7 to about 11 wt %, based upon the total weight ofthe alloy. In one embodiment, it is desirable to have a shape memoryalloy that displays superelasticity and/or pseudoelasticity, which has amolybdenum equivalent of about 7.5 to about 10.5 wt %, based upon thetotal weight of the alloy. In another embodiment, it is desirable tohave a shape memory alloy that displays superelasticity and/orpseudoelasticity, which has a molybdenum equivalent of about 8 to about10 wt %, based upon the total weight of the alloy. In yet anotherembodiment, it is desirable to have a shape memory alloy that displayssuperelasticity and/or pseudoelasticity, which has a molybdenumequivalent of about 8.5 to about 9.8 wt %, based upon the total weightof the alloy.

[0055] In one embodiment, the elements present in equation (1) and/or(2) may be optional if desired. In another embodiment, the elements thatmay be present in the composition in addition to titanium aremolybdenum, vanadium, chromium, aluminum, and/or niobium. In yet anotherembodiment, it is generally desirable for the elements represented inequations (2) to be present in the composition in amounts of greaterthan or equal to about 0.1, preferably greater than or equal to about0.5, preferably greater than or equal to about 1, preferably greaterthan or equal to about 1.5, preferably greater than or equal to about 5,and preferably greater than or equal to about 10 wt %, based upon thetotal weight of the alloy composition. In yet another embodiment, it isgenerally desirable for the elements represented in equations (2) to bepresent in the composition in amounts of less than or equal to about 50,preferably less than or equal to about 40, preferably less than or equalto about 35, preferably less than or equal to about 30, preferably lessthan or equal to about 25, and preferably less than or equal to about 20wt %, based upon the total weight of the alloy composition.

[0056] Titanium alloys having a high enough concentration of βstabilizers, generally are sufficiently stable to have a meta-stable βphase structure at room temperature. The alloys showing such a propertyare called β titanium alloys. Martensite transformations are commonlyfound among β titanium alloys. The martensitic transformationtemperature in β titanium alloys generally decreases with an increasingamount of β stabilizer in the alloy, while increasing the amount of αstabilizer generally raises the martensitic transformation temperature.Therefore, depending on the extent of stabilization, β titanium alloysmay exhibit a martensitic transformation when cooled rapidly fromtemperatures greater than those at which the β phase is the single phaseat equilibrium. The β titanium alloy generally comprises an amount ofabout 8 to about 10 wt % of molybdenum, about 2.8 to about 6 wt %aluminum, up to about 2 wt % chromium, up to about 2 wt % vanadium, upto about 4 wt % niobium, with the balance being titanium. All weightpercents are based on the total weight of the alloy. Within theaforementioned range for molybdenum, it is generally desirable to havean a mount of greater than or equal to about 8.5, preferably greaterthan or equal to about 9.0, and more preferably greater than or equal toabout 9.2 wt % molybdenum. Also desirable within this range is an amountof less than or equal to about 9.75, and more preferably less than orequal to about 9.5 wt % molybdenum, based on the total weight of thealloy.

[0057] Within the aforementioned range for aluminum, it is generallydesirable to have an amount of greater than or equal to about 2.85,preferably greater than or equal to about 2.9, and more preferablygreater than or equal to about 2.93 wt % aluminum. Also desirable withinthis range is an amount of less than or equal to about 5.0, preferablyless than or equal to about 4.5, and more preferably less than or equalto about 4.0 wt % aluminum, based on the total weight of the alloy.

[0058] Within the aforementioned range for vanadium, it is generallydesirable to have an amount of greater than or equal to about 1,preferably greater than or equal to about 1.2, and more preferablygreater than or equal to about 1.5 wt % vanadium, based on the totalweight of the alloy.

[0059] Within the aforementioned range for niobium, it is generallydesirable to have an amount of greater than or equal to about 2,preferably greater than or equal to about 3, and more preferably greaterthan or equal to about 3.5 wt % niobium, based on the total weight ofthe alloy.

[0060] In one exemplary embodiment, it is generally desirable for the βtitanium alloy to comprise 8.9 wt % molybdenum, 3.03 wt % aluminum, 1.95wt % vanadium, 3.86 wt % niobium, with the balance being titanium.

[0061] In another exemplary embodiment, it is generally desirable forthe β titanium alloy to comprise 9.34 wt % molybdenum, 3.01 wt %aluminum, 1.95 wt % vanadium, 3.79 wt % niobium, with the balance beingtitanium.

[0062] In one embodiment, the β titanium alloy may be solution treatedand/or thermally aged. In solution treating the β titanium alloy, thealloy is subjected to a temperature greater than or equal to about 850°C., the β transus temperature for the alloy. The solution treatment ofthe alloy is normally carried out in either vacuum or inert gasenvironment at a temperature of about 850 to about 1000° C., preferablyabout 850 to about 900° C., for about 1 minute or longer in durationdepending on the mass of the part. The heating is followed by a rapidcooling at a rate greater than or equal to about 5° C./second,preferably greater than or equal to about 25° C./second, and morepreferably greater than or equal to about 50° C./second, by using aninert gas quench or air cooling to retain a fully recrystallized singlephase β grain structure. In some instances, it is preferred that thequenched alloy is subsequently subjected to an ageing treatment at about350 to about 550° C. for about 10 seconds to about 30 minutes to adjustthe amount of a fine precipitate of the ω phase. In another embodiment,it is desirable to subject the alloy to heat treatment for a time periodof up to 8 hours at temperatures of about 350 to about 550° C.

[0063] In another embodiment, the β titanium alloy may be solutiontreated at a temperature below the β transus temperature of about 750 toabout 850° C., preferably about 800 to about 850° C., for about 1 toabout 30 minutes to induce a small amount of ≢0 precipitates in therecrystallized β matrix. The amount of the α precipitates is preferablyless than or equal to about 15 volume percent and more preferably lessthan or equal to about 10 volume percent, based on the total volume ofthe composition. This improves the tensile strength to an amount ofgreater than or equal to about 140,000 pounds per square inch (9,846kilogram/square centimeter).

[0064] The β titanium alloy in the solution treated condition mayexhibit pseudoelasticity. The solution treated β titanium alloygenerally exhibits a pseudoelastic recovery of greater than or equal toabout 75% of the initial strain when elastically deformed to a 2%initial strain, and greater than or equal to about 50% of the initialstrain when elastically deformed to a 4% initial strain. The initialstrain is the ratio of the change in length to the original length ofthe alloy composition.

[0065] The β titanium alloy in the solution treated condition mayexhibit linear elasticity. The solution treated β titanium alloygenerally exhibits a linear elastic recovery of greater than or equal toabout 75% of the initial strain when elastically deformed to a 2%initial strain, and greater than or equal to about 50% of the initialstrain when elastically deformed to a 4% initial strain. The initialstrain is the ratio of the change in length to the original length ofthe alloy composition.

[0066] In another embodiment, the β titanium alloy may be cold worked byprocesses such as cold rolling, drawing, swaging, pressing, and thelike, at ambient temperatures. The β titanium alloy may preferably becold worked to an amount of about 5 to about 85% as measured by thereduction in cross-sectional area based upon the original crosssectional area. Within this range it is desirable to have a crosssectional area reduction of greater than or equal to about 10,preferably greater than or equal to about 15% of the initial crosssectional area. Also desirable within this range is a reduction in crosssectional area of less than or equal to about 50, more preferably lessthan or equal to about 30% based on the initial cross-sectional area.The β titanium alloy in the cold worked state (also referred to as thework hardened state) exhibits linear superelasticity where greater thanor equal to about 75% of the initial strain is elastically recoverableafter deforming to a 2% initial strain, and greater than or equal toabout 50% of the initial strain is elastically recoverable afterdeforming to a 4% initial strain. In one exemplary embodiment related tocold working, the elastic modulus of the β titanium alloy is reducedthrough cold working by an amount of greater than or equal to about 10,preferably greater than or equal to about 20 and more preferably greaterthan or equal to about 25% based upon the elastic modulus, after thealloy is heat treated.

[0067] In one exemplary embodiment related to cold working, the elasticmodulus of the β titanium alloy is reduced through cold working by anamount of greater than or equal to about 10, preferably greater than orequal to about 20 and more preferably greater than or equal to about 25%based upon the elastic modulus after the alloy is heat treated.

[0068] It is generally desirable to use shape memory alloys havingpseudo-elastic properties, and which are formable into complex shapesand geometries without the creation of cracks or fractures. In oneembodiment, the β titanium alloy having linear elastic, linearlysuperelastic, pseudoelastic or superelastic properties may be used inthe manufacturing of various articles of commerce. Suitable examples ofsuch articles are eyewear frames, face inserts or heads for golf clubs,medical devices such as orthopedic prostheses, spinal correctiondevices, fixation devices for fracture management, vascular andnon-vascular stents, minimally invasive surgical instruments, filters,baskets, forceps, graspers, orthodontic appliances such as dentalimplants, arch wires, drills and files, and a catheter introducer (guidewire).

[0069] In one embodiment, the β titanium alloy having pseudoelastic orsuperelastic properties may be used in the manufacturing of variousarticles of commerce. Suitable examples of such articles are eyewearframes, face inserts or heads for golf clubs, medical devices such asorthopedic prostheses, spinal correction devices, fixation devices forfracture management, vascular and non-vascular stents, minimallyinvasive surgical instruments, filters, baskets, forceps, graspers,orthodontic appliances such as dental implants, arch wires, drills andfiles, and a catheter introducer (guide wire). Advantages provided bythe β titanium alloys are that they are free of nickel, having lowmodulus, flexible and can be welded, brazed or soldered if desired.

[0070]FIG. 1 illustrates a typical eyewear frame 100. Frame 100 includesa pair of rims 110, a bridge 120, a pair of temples 130, and a pair ofhinges 140. Rims 110 are joined by bridge 120, which is generallyattached to rims 110 by brazing or welding 150. Temples 130 are attachedto the hinges 140 by brazing or welding 170, and the hinges 140 areattached to the temples 130. All metal parts of the frame 100 may beformed using β titanium alloys. The β titanium alloys generally providea lightweight frame with increased spring-back characteristics thanconventional titanium alloy frames but with improved adjustability thana superelastic NiTi (nickel titanium) frame. Alternatively, any one ormore of the metal parts of the frame 100 may be formed from β titaniumalloys. The use of superelastic β titanium alloy is generally preferredin components that require flexibility and adjustability, such as thetemples 130. Other components of the frame 100 may be formed usinglinearly elastic (LE) P titanium alloy, other titanium alloys such asTi-6Al-4V or commercially pure titanium, other metallic alloys such asstainless steel, CuNi (copper-nickel) alloy or polymeric materials.

[0071] In an alternative embodiment, the temples 130 are formed from asuperelastic β titanium alloy, which may be directly connected to thelenses (not shown) of the completed eyewear, thereby eliminating theneed for rims 110 and hinges 140. In yet another alternative embodiment,the superelastic β titanium alloy eyewear may be manufactured bystamping or cutting out the shape of the eyewear frame 100 from a sheetof β titanium alloy, thereby forming a single piece. The piece is thenformed into a contour of the frame and heat treated. Groves are thenmachined along the edges of the rim 110 to fit lens.

[0072] In yet another embodiment, at least a portion of the framecomprises a linearly superelastic β titanium alloy, while anotherportion of the frame comprises a linear elastic (LE) β titanium alloys,other titanium alloys such as Ti-6Al-4V or commercially pure titanium,other metallic alloys such as stainless steel, nickel silver alloy or apolymeric resin. When it is desirable to have a portion of the framecomprising a linearly superelastic β titanium alloy, the desired portionis generally cold worked by rolling, drawing, swaging, pressing, or thelike.

[0073] Polymeric resins used in the eyewear frames may comprisethermoplastic resins, thermosetting resins, blends of thermoplasticresins with thermosetting resins. In general, the polymeric resin may bederived from a suitable oligomer, polymer, block copolymer, graftcopolymer, star block copolymer, dendrimers, ionomers having a numberaverage molecular weight (Mn) of about 1000 grams per mole (g/mole) toabout 1,000,000 g/mole. Suitable examples of thermoplastic resinsinclude polyacetal, polyacrylic, styrene acrylonitrile,acrylonitrile-butadiene-styrene, polycarbonates, polystyrenes,polyethylene, polypropylenes, polyethylene terephthalate, polybutyleneterephthalate, polyamides such as nylon 6, nylon 6,6, nylon 6,10, nylon6,12, nylon 11 or nylon 12, polyamideimides, polybenzimidazoles,polybenzoxazoles, polybenzothiazoles, polyoxadiazoles, polythiazoles,polyquinoxalines, polyimidazopyrrolones, polyarylates, polyurethanes,thermoplastic olefins such as ethylene propylene diene monomer, ethylenepropylene rubber, polyarylsulfone, polyethersulfone, polyphenylenesulfide, polyvinyl chloride, polysulfone, polyetherimide,polytetrafluoroethylene, fluorinated ethylene propylene, perfluoroalkoxypolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylfluoride, polyetherketone, polyether etherketone, polyether ketoneketone, or the like, or combinations comprising at least one of theforegoing thermoplastic resins.

[0074] Suitable examples of blends of thermoplastic resins includeacrylonitrile-butadiene-styrene/nylon,polycarbonate/acrylonitrile-butadiene-styrene, acrylonitrile butadienestyrene/polyvinyl chloride, polyphenylene ether/polystyrene,polyphenylene ether/nylon, polysulfone/acrylonitrile-butadiene-styrene,polycarbonate/thermoplastic urethane, polycarbonate/polyethyleneterephthalate, polycarbonate/polybutylene terephthalate, thermoplasticelastomer alloys, nylon/elastomers, polyester/elastomers, polyethyleneterephthalate/polybutylene terephthalate, acetal/elastomer,styrene-maleicanhydride/acrylonitrile-butadiene-styrene, polyetheretherketone/polyethersulfone, polyethylene/nylon,polyethylene/polyacetal, or the like, or combinations comprising atleast one of the foregoing thermoplastic blends.

[0075] Suitable examples of polymeric thermosetting materials includepolyurethanes, natural rubber, synthetic rubber, epoxy, phenolic,polyesters, polyamides, silicones, or the like, or combinationscomprising at least one of the foregoing.

[0076] For the frame 100, it is generally desirable to have the temples130 manufactured from superelastic or linearly superelastic β titaniumalloy. While many variations of temple 130 are available in the eyewearmanufacturing industry, the temple 130 is shown in FIG. 2 one possibleconstruction. The temple 130 includes a tapered end 210, a pressed end220, a hinge 140, a rim connector 240, and a hinge cut 250.

[0077] In temple 130, the tapered end 210 and the pressed end 220 areformed from a continuous piece of β titanium alloy wire. The hinge 140and the rim connector 240 are each joined to the pressed end 220,typically by brazing. Hinge cut 250 generally permits a free rotation ofthe hinge 140. The hinge 140 and the rim connector 240 may also befabricated from β titanium alloys or from other suitable material suchas titanium or nickel silver alloys, if desired.

[0078] The superelastic β titanium alloy generally provides an adequatespring-back for eyewear applications. It is generally desired to usesuperelastic β titanium alloy having a minimum recovery of about 50%,based on the outer fiber bend strain, when the alloy is deformed to anouter fiber strain of about 4%. Within this range, it is more preferablygreater than or equal to about 75%, when the alloy is deformed to about4% outer fiber strain.

[0079] It is also generally desirable for the superelastic β titaniumalloy to have a minimum recoverable strain of about 2%, based on theoriginal length when the alloy is deformed to about 4% in tensilestrain. Within this range, it is generally desired to have a minimumrecovery of greater than or equal to about 3% when the alloy is deformedto about 4% tensile strain in the tensile test.

[0080] The eyewear frame may be manufactured by a variety of differentmethods used to shape or form metals and alloys. In one embodiment, thedesired shape of the eyewear frame 100 is stamped from a sheet of βtitanium alloy, thereby forming a single piece. In another embodiment,the basic shape may be formed of wires using mechanical shaping methods.

[0081] For example, in the manufacture of temple 130, a β titanium alloywire is modified to provide the basic shape of temple 130. Thesuperelastic β titanium alloy wire is first swaged, creating multiplesections having consecutively decreasing diameters, and then a number ofthe largest sections are pressed to flatten them. The eyewear frame 100can also be fabricated from wires via cold forming and shape-settingheat treatment processes. The eyewear frame 100 can also be fabricatedfrom superelastic β titanium alloys sheets or wires by laser cutting,chemical etching or other cutting means followed by shape-setting heattreatment or other forming and heat treating processes.

[0082] The eyewear frame 100 may optionally be annealed to regainworkability and to overcome brittleness induced by cold working. Coldworking of β titanium alloys (e.g., swaging, pressing) generally alterits mechanical properties, causing it to become stronger and morebrittle. Annealing at temperatures of greater than or equal to about850° C. for about 1 to about 30 minutes may be used to soften thematerial, rendering it more ductile and formable.

[0083] Following the manufacturing of the eyewear frame 100 and theoptional annealing, it may be desired to attach additional components tothe frame. For example, in a general eyewear manufacturing process, thehinge 140 and the rim connector 240 are brazed or soldered to the temple130, and the temple 130 may be cut to permit the hinge 140 to rotate.

[0084] Where desired, the eyewear frame 100 may be subjected to apolishing operation in order to give the frame a smooth appearance andto remove any rough edges. For example, the eyewear frame 100 can bepolished by high energy barrel tumbling and then plated by processessuch as chemical vapor deposition, electroplating, and the like, toprepare the frame for additional finishing steps. This plating ispreferably accomplished using gold or nickel.

[0085] After the plating operation, the eyewear frame 100 may beoptionally heat-treated at a temperature of about 350 to about 450° C.for a period of about 10 minutes in order to infuse the gold or nickellayer deposited on the frame into the β titanium alloy. The eyewearframe is then be subjected to additional finishing processes to providea desirable aesthetic appearance. For example, the frame may be platedwith a metal, such as gold, chrome, or platinum. A protective coating,such as a light spray of epoxy, may be added to seal and protect theframe. If desired, the frame is subjected to adjustments by the user tofurther shape the eyewear frame 100.

[0086] In another embodiment, the β titanium alloy may be used tomanufacture at least a portion of a golf club. The β titanium alloy maybe also be used to manufacture a golf club head. In an exemplaryembodiment, the β titanium alloy may be used to manufacture faceinserts, which are mounted into the golf club head.

[0087]FIG. 3A shows an insert 2 that substantially follows the contoursof the golf club head. The bevel is designed such that when the insertis mounted into the golf club head mating cutout or pocket, the insertwill be retained securely in the club head even during the violentswings encountered while playing golf. The bevel is generally at anangle of about 30 to about 60 degrees with respect to a perpendicular tothe back 8 of the insert and extends around the bottom and the two sidesadjacent to the bottom edge of the insert 2 as shown in FIG. 3A. Theinsert 2 generally has a thickness of about 0.010 (0.0254 centimeter) toabout 0.93 inches (2.36 centimeters). In an exemplary embodiment, theinsert may have a variable thickness across its cross section ifdesired.

[0088]FIG. 3B shows another embodiment of the insert. Here a tongue 9 isformed on opposing sides of the insert to secure the insert in acorresponding groove in the golf club head. FIG. 4A shows a pocket 12formed in the face of a club head 14 into which an insert 2 havingbeveled edges may be disposed. The pocket is formed from the bottom ofthe club head and extends upward. However, the pocket does not extend tothe top edge of the club head, there remains a narrow channel 16 betweenthe top of the pocket and the top of the golf club head. The insert ispreferably wedge shaped and the angle is preferably about 2 degrees.

[0089] Referring to FIG. 4B the pocket in the golf club head has agrooved edge 18 that extends around the three sides (left, right andtop) of the pocket. The groove 18 is arranged to be in mechanicalcommunication with the tongue 9 of an insert. The insert may be securedwithin the club head by cement, polymeric resins such as epoxy,acrylates, methacrylates, silicones, or the like. FIG. 5 shows anothergolf club head 20 with an insert 22 that extends from the top to thebottom of the golf club head 20. In this instance, the bottom and topedges of the insert are flush with the bottom and top edge of the golfclub head 20. Grooved edges 24 may be used to retain the insert 2 in thegolf club head 20.

[0090]FIG. 6A provides a front view of a golf club face 40 with theinsert 42. The insert 42 covers the striking area of the golf club headand the golf club head 44 forms a margin around the insert. FIG. 6Bshows one configuration of the cross sectional view of the golf clubhead 44 as a casting. Forged and machined golf club heads 44 may also beused. The golf club head 44 has a cavity 46 into which the insert 42 isplaced. Ears 48 extend out from the golf club head 44 as shown and theinserts have grooves 50 designed to receive the ears. The ears areswaged over into the grooves as shown in FIG. 6C. The rough edges maythen be finished to form a golf club head 44 having a smooth club faceas shown in FIG. 6D.

[0091] In one embodiment related to the assembly of the insert into thegolf club head in FIGS. 3A, 3B, 4A, 4B, 5, 6A-D, the insert may be heldin place in a slot in the golf club head through friction or othermechanical means. When friction is employed, the insert is held inposition in the golf club head via a tight toleranced fit. In anexemplary embodiment, the insert is assembled in the golf club head viabrazing or welding. This facilitates ease of manufacture and assembly ofthe golf club head when compared with other methods of manufacturing.

[0092] In another embodiment, the β titanium alloy may be used may beused in a catheter having an implantable stent as shown in FIG. 26. Inthe FIG. 26, the distal end of a catheter 115 having a stent 165 carriedwithin it for implantation into the body of a patient. The proximal endof the catheter 115 is connected to a suitable delivery mechanisms andthe catheter 115 is of sufficient length to reach the point ofimplantation of the stent 165 from the introduction point into the body.As used herein, the term “proximal” refers to a location on the catheterclosest to the clinician using the device and thus furthest from thepatient on which the device is used. Conversely, the term “distal”refers to a location farthest from the clinician and closest to thepatient.

[0093] The catheter 115 includes an outer sheath 105, a middle tube 125which may be formed of a compressed spring, and a flexible (e.g.,polyamide) inner tube 145. A stent 165 for implantation into a patientis carried within the outer sheath 105. The stent 165 is generallymanufactured from a shape memory alloy frame 185, which is formed in acriss-cross pattern, which may be laser cut. One or both ends of thestent 165 may be left uncovered as illustrated at 225 and 245 to provideanchoring within the vessel where the stent 165 is to be implanted.

[0094] A radiopaque atraumatic tip 265 is generally secured to the endof the inner tube 145 of the catheter. The atraumatic tip 265 has arounded end and is gradually sloped to aid in the movement of thecatheter through the body vessel. The atraumatic tip 265 is radiopaqueso that its location may be monitored by appropriate equipment duringthe surgical procedure. The inner tube 145 is hollow so as toaccommodate a guide wire, which is commonly placed in the vessel priorto insertion of the catheter, although a solid inner section and be usedwithout a guide wire. Inner tube 145 has sufficient kink resistance toengage the vascular anatomy without binding during placement andwithdrawal of the delivery system. In addition, inner tube 145 is ofsufficient size and strength to allow saline injections without rupture.

[0095] A generally cup-shaped element 285 is provided within thecatheter 115 adjacent the rear end of the stent 165 and is attached tothe end of the spring 125 by appropriate means, e.g., the cup element285 may be plastic wherein the spring 125 is molded into its base, orthe cup element 285 may be stainless steel wherein the spring 125 issecured by welding or the like. The open end of the cup element 285serves to compress the end 245 of the stent 165 in order to provide asecure interface between the stent 165 and the spring 125.Alternatively, instead of a cup shape, the element 285 could be formedof a simple disk having either a flat or slightly concave surface forcontacting the end 245 of the stent 165.

[0096] In yet another embodiment, the β titanium alloy may be utilizedas an intravenous (IV) catheter to introduce certain fluids such assaline solution directly into the bloodstream of a patient. Typically, aneedle or other stylet made from the β titanium alloy is firstintroduced through the cannula portion of the catheter and into the skinof the patient at the desired location such as the back of the patient'shand or a vessel on the inside of the arm. Once insertion is complete,the needle is removed from the cannula portion of the catheter. Afterremoving the needle, a fluid handling device such as a syringe isattached to the luer fitting located at the proximal end of the catheterhub. Fluid then flows directly from the fluid handling device throughthe catheter into the bloodstream of the patient. When the needle isremoved from the cannula, the health care worker must place the exposedneedle tip at a nearby location while simultaneously addressing the taskrequired to accomplish the needle removal. It is at this juncture thatthe exposed needle tip creates a danger of an accidental needle stickoccurring which leaves the health care worker vulnerable to thetransmission of various, dangerous blood-borne pathogens such as humanimmune virus (HIV) and hepatitis.

[0097] As used herein, the term “proximal” refers to a location on thecatheter and needle assembly with needle tip protector closest to theclinician using the device and thus furthest from the patient on whichthe device is used. Conversely, the term “distal” refers to a locationfarthest from the clinician and closest to the patient.

[0098] As illustrated in FIGS. 27 and 28, the IV catheter assembly 201comprises catheter assembly 221 and needle assembly 241. Needle assembly241 further includes protector 261. Catheter assembly 221 includescatheter 281, which is a tubular structure having a proximal end 311 anddistal end 291. Proximal end 311 of catheter 281 is fixedly attached tocatheter hub 301. Catheters are well known in the medical art and one ofmany suitable materials, most of which are flexible thermoplastics, maybe selected for use in catheter 281. Such materials may include, forexample, polyurethane or fluorinated ethylene propylene. Catheter hub301 is a generally tubular structure having an internal cavity in fluidcommunication with the internal lumen of catheter 281. Catheter hub 301may be made from a suitable, rigid medical grade thermoplastic such as,for example, polypropylene or polycarbonate. For illustration purposescatheter hub 301 is shown translucent, though in actual use it may betranslucent or opaque. At the proximal end of catheter hub 301 isintegrally attached Luer fitting 321. Luer fitting 321 provides forsecure, leak proof attachment of tubing, syringes, or any of many othermedical devices used to infuse or withdraw fluids through catheterassembly 221. As shown in FIGS. 27 and 28, retainer 601, which islocated approximately mid way between the proximal end and distal end ofsidewall 361 and fixedly attached thereto, includes aperture 621 whichis an opening therethrough. Retainer 601 is generally a doughnut shapedwasher made of a material such as, for example, silicone orpolytetrafluoroethylene. The retainer 601 generally secures theprotector 261 in catheter hub 301.

[0099] Referring again to FIGS. 27 and 28, needle assembly 241 comprisesneedle 381, which is a tubular structure with proximal end 391 anddistal end 411, needle hub 401, and protector 261. Protector 261 isassembled slidably on needle 381. Needle 381, which is preferably madeof stainless steel has a lumen therethrough created by its innerdiameter. Proximal end 391 of needle 381 is fixedly attached to needlehub 401. Bevel 421, which is located at distal end 411 of needle 381creates a sharp piercing tip. Needle groove 441, which includes proximalwall 431 and distal wall 451, is located at distal end 411 of needle 381proximal to bevel 421 and is smaller in diameter than the nominal outerdiameter of needle 381. Needle groove 441 may be created by machinegrinding around the outside diameter of needle 381 resulting in anannular channel between its nominal outer diameter and inner diameter.The resulting groove 441 is smaller in dimension than the nominal outerdiameter of needle 381 but greater in dimension that the lumen in needle381 and generally prevents the complete removal of protector 261 fromneedle 381. In the preferred embodiment, the dimension across groove 441is about 0.002 to about 0.003 inches (about 0.0508 to about 0.0762millimeter) smaller than the dimension of the nominal outer diameter ofneedle 381, dependent upon needle “gauge” size.

[0100] Needle hub 401 is generally a tubular structure having aninternal cavity in fluid communication with the lumen in needle 381. Itis preferably made of a translucent or transparent generally rigidthermoplastic material such as, for example, polycarbonate. At the mostproximal end of the internal cavity in needle hub 401 is fixedlyattached a porous plug 461. A flashback chamber 481 is created in thecavity distal to porous plug 461. Porous plug 461 contains a pluralityof microscopic openings, which are large enough to permit the passage ofair and other gasses but small enough to prevent the passage of blood.Flashback chamber 481 fills with blood upon successful entry of theneedle tip into the targeted vein, providing the clinician visualconformation of the correct placement of the needle.

[0101] In one embodiment, the β titanium alloy may be used as anorthopedic device such as a fixation device for bones in the hip, knee,spine, or the like. A suitable example of one configuration of a bonefixation device shown in FIGS. 29, 30 and 31 is a threaded bone screw.FIGS. 29, 30 and 31 show a cannulated, internally and externallythreaded bone screw 202 and a cannulated driver device 222 constructedfrom a β titanium alloy. The driver device 222 includes a shaft member262 defining a throughgoing bore 272, a handle 282 and includes a rod302 and a cap member 322. The rod 302 and cap member 322 are used toreleaseably secure the bone screw 202 to the driver device 222 as willlater be described. The shaft member 262 is an elongated, generallycylindrical structure, which has a cylindrical throughgoing bore orcannula 272 best seen in the cross-sectional view of FIG. 31 whichextends longitudinally from a proximal end 342 of the shaft member 262to a distal end 362.

[0102] The shaft member 262 is an integral tubular structure preferablyconstructed of surgical steel, although any suitable material such as βtitanium alloy can be used, and includes a shaped engagement structure382 integrally formed at the distal end 362 and one or more annulargrooves 372 spaced along its length. The engagement structure 382, whichpreferably has a hexagonal configuration facilitates the mating androtational engagement of the bone screw 202 with the driver as will bedescribed and the grooves 372 may be used as attachment sites forconventional clamp members during a bone fixation procedure. It will beappreciated that the engagement structure 382 may take any angularconfiguration such as square, octagonal or the like and canalternatively engage the outer periphery of the screw head.

[0103] The handle 282 has a throughgoing bore 392 to receive theproximal end 342 of the shaft member 262 and is preferably constructedof wood or plastic. The handle 282 is secured to the shaft member 262 bysecuring the handle sections together with conventional rivets 392 or byother suitable means. The rivets do not extend into or through the boreof the shaft member 262. Alternatively, the handle member 282 may beremovably mounted to the shaft member 262.

[0104] The rod 302 is an integral, solid, generally cylindricalstructure preferably constructed of surgical or high grade steel and isprovided with a threaded section 422 at its distal end and a machinedrecess or well 44 near its proximal end which receives set screw 472.The cap member 322 is a generally cylindrical structure that has a blindbore 432 to receive the proximal end of the rod 302 and a cylindrical,internally threaded passage 452 which extends from a side surface of thecap member 322 into the blind bore 432 to permit the passage of aconventional set screw 472 having an Allen head. A conical end portionof the Allen set screw is received within the well 44 in the rod 30 tolock the cap member 322 to the rod 302. The outer surface of cap 322 isknurled at 332 to allow the cap 322 and secured rod 302 to be rotatedwithin bore 272 of the shaft 262 so that threaded end 422 can be screwedinto the inner thread 582 of the cannulated bone screw 202.

[0105] The outer diameter of the cylindrical rod 302 is less than theinner diameter of the cylindrical bore 272 in the shaft member 262 sothat the rod 302 can be easily received therein and pass therethrough.Conversely the threaded end section 422 has threads with an outerdiameter greater than the outer diameter of bore 272 so that rod 302cannot be pulled through the bore 272 of the shaft 262. When the capmember 322 is releaseably locked to the proximal end of the rod 302, capmember 322 prevents a portion of the proximal end of the rod 302 fromentering the cannula 272 of the shaft member 262. As best seen in FIG.31, the rod 302 is longer than the shaft member 262 so that when the capmember 322 is mounted on the rod 302 and the rod 302 is disposed withinthe cannula or bore 272 of the shaft member 262, the threaded section422 of the rod 302 extends a predetermined length beyond the distal end362 of the shaft member 262 to threadedly engage the internal threading582 of the bone screw 202. The orthodontic device may be advantageouslyused in other body tissue in all living beings. Other examples oforthodontic devices are those, which may be used in hip, kneel, shoulderimplants, intermedullary rods and nails, fracture fixation devices,spinal fusion and correction instruments.

[0106] In another embodiment, the β titanium alloy may be used inorthodontic devices such as orthodontic arch wires. One possibleconfiguration of an orthodontic arch wire 103 is shown in FIGS. 32 and33, and includes an anterior segment 113, and a pair of posteriorsegments 123 and 133 secured to and extending from the respective endsof the anterior segment. The anterior segment may be made of a materialhaving a stiffness or flexural rigidity, which is less than that of thematerial forming the posterior segments. The segments can be securedtogether by using any of several different attachment techniques. In theform shown in FIGS. 32 and 33, a crimpable metal tube 153 is provided ateach segment junction for mechanical attachment of the segments. Asshown in FIG. 32, the β titanium alloy arch wire 103 is of conventionalgenerally U-shaped configuration for conformation with the patient'sdental arch. The arch is equally useful with lingual brackets andrelated appliances, which are mounted on the rear surfaces of the teeth.FIG. 34 shows a so-called “mushroom” arch wire 203, which is again ofgenerally U-shaped configuration, but is contoured to conform to thecurvature of the lingual or inner surfaces of the teeth. Arch wire 203includes an anterior segment 213 of relatively low stiffness, a pair ofposterior segments 223 and 233 of relatively higher stiffness, andcrimped tubes 243 joining the segments and positioned to be just distalof the cuspids when installed. Other dental applications include archwires, dental implants, files and drills used in orthodontic work.

[0107] The β titanium alloy has a number of advantages. The elasticmodulus of the β titanium alloy is advantageously reduced through coldworking by an amount of greater than or equal to about 10, preferablygreater than or equal to about 20 and more preferably greater than orequal to about 25% based upon the elastic modulus after the alloy isheat treated. The β titanium alloy may preferably be cold worked to anamount of about 5 to about 85% as measured by the reduction incross-sectional area based upon the original cross sectional area.Within this range it is desirable to have a cross sectional areareduction of greater than or equal to about 10, preferably greater thanor equal to about 15% of the initial cross sectional area. Alsodesirable within this range is a reduction in cross sectional area ofless than or equal to about 50, more preferably less than or equal toabout 30% based on the initial cross-sectional area. When cold worked,the β titanium alloy may have a pseudoelastic strain recovery of greaterthan or equal to about 75% of the applied strain, when the appliedstrain is up to about 2% of the original length and of greater than orequal to about 50% of the applied strain, when the applied strain is upto about 4% of the original length. (i.e., the change in length is 4% ofthe original length).

[0108] The following examples, which are meant to be exemplary, notlimiting, illustrate the methods of manufacturing for some of thevarious embodiments of the articles prepared from the β titanium alloysdescribed herein.

EXAMPLES Example 1

[0109] All of the sample alloys discussed below were prepared by adouble vacuum arc melting technique. The ingots were hot rolled andflattened to sheets having a thickness of 1.5 millimeter (mm). Thesheets were then heat treated at 870° C. for 30 minutes in air and aircooled to ambient temperature. Oxides on the sheets were removed bydouble-disc grinding and lapping to a thickness of 1.3 mm. Heat agingexperiments were conducted at 350° C. using a nitride/nitrate salt bath.

[0110] Permanent deformation and pseudo-elastic recovery strains weredetermined using bend tests. Specimens having dimensions 0.51 mm×1.27mm×51 mm were cut from the sheets. The specimens were bent against a rodof approximately 12.2 mm in diameter to form a “U” shape to yield anouter fiber or outer surface strain close to 4%. The angles between thestraight portions were measured afterwards and the strain recoverycalculated by using the formula:

e(rec)−e(180−a)/180;

[0111] where “a” is the unrecovered angle and “e” is the outer-fiberbending strain.

[0112] Tensile strain recovery was measured by tensile elongation to astrain of 4% followed by unloading to zero stress. Tensile specimenswith a cross sectional dimension of 0.90 mm×2.0 mm were used and thestrain was monitored using an extensometer. An environmental chamberwith electrical heating and CO₂ cooling capabilties provided a testingcapability from −30° C. to 180° C.

[0113] Nine β titanium alloys having the compositions listed in Table 1were examined. The percentage of the elastic recovery strain withrespect to the total bend strain was measured for comparison. TABLE 1Sample # Titanium Molybdenum Niobium Vanadium Aluminum 1 Balance 7.633.98 2.05 3.10 2 Balance 8.03 3.89 2.03 3.09 3 Balance 8.40 3.83 1.943.03 4 Balance 8.97 3.86 1.95 3.03 5 Balance 9.34 3.79 1.95 3.01 6Balance 10.35 3.83 1.99 3.02 7 Balance 10.83 3.88 2.01 3.02 8 Balance11.48 4.00 2.04 3.15 9 Balance 11.68 3.89 1.98 3.07

[0114] In the Table 1 above Sample 1 and Samples 6-9 are comparativeexamples. The results of elastic recovery after bending to approximately4% outer fiber strain is graphically demonstrated in FIG. 7. The figureshows a maximum elastic strain recovery at about 9 wt % molybdenum,where the alloy after solution heat treatment and subsequent aircooling, exhibits an elastic recovery strain of approximately 80% of theapplied 4% deformation strain. Increasing or decreasing the molybdenumcontent from 9 wt % generally results in decreasing elastic recovery. Itmay also be seen that an aging treatment at 350° C. for a short durationof 10 seconds results in an improved elastic recovery, for titaniumalloys having a molybdenum content between 8.4 and 11 wt %. The optimalelastic strain recovery after heat aging at 350° C. for 10 seconds forthe alloy having about 9 wt % molybdenum is approximately 90% of theapplied 4% bend strain. Alloys with a molybdenum content less than 8.4wt % exhibit a different aging characteristic. Aging at 350° C. maydegrade elastic strain recovery as for alloy 2 having about 8.03 wt %molybdenum, or has no significant effect as for alloy 1 having about7.63 wt % molybdenum.

[0115] The percent of the elastic recovery to the total deformationduring thermal aging at 350° C. for Samples 4, 5 and 6 respectively, areplotted in the FIGS. 8, 9 and 10 respectively. From the FIGS. 8, 9 and10 it may be seen that the elastic recoveries of all three alloys reacha maximum after aging for about 10 to about 60 seconds. Aging beyond 15minutes (900 seconds) degrades the elastic recovery.

[0116] The percents of the elastic recovery to the total deformationduring thermal aging at about 250 to about 550° C. for 10 seconds forSamples 4 and 5 respectively are plotted in the FIGS. 11 and 12,respectively. An optimal for Sample 4 appears at 350° C., which improvesthe elastic recovery to a percentage close to 90% while aging attemperatures equal to or higher than 400° C. degrades elastic recoveryto about 40%. For Sample 5, aging in this temperature range generallyimproves the elastic recovery. The maximum improvement occurs at about450° C. where the elastic recovery is improved to 90%.

[0117] The alloys shown in Table I also exhibit linear superelasticityafter cold working with a reduction of greater than or equal to about30% in the cross-sectional area. For example, a wire fabricated from aningot having a composition of 11.06 wt % molybdenum, 3.80 wt % niobium,1.97 wt % vanadium, 3.07 wt % aluminum with the remainder being titaniumexhibited an elastic recovery strain of 3.5% after bending to a totaldeformation of 4% outer fiber strain, when the reduction in the crosssectional area after cold working was 84%.

Example 2

[0118] In this example, the β titanium alloys were manufactured bydouble vacuum arc melting. Chemistries of the alloys were analyzed usinginductively coupled plasma optical emission spectrometry (ICP-OE). Theresults are tabulated in Table 2. The ingot was hot-forged, hot-rolledand finally cold-drawn to wire of various diameters in the range ofabout 0.4 to about 5 mm. Inter-pass annealing between cold reductionswas carried out at 870° C. in a vacuum furnace for wires having adiameter of larger than 2.5 mm or by strand annealing under inertatmosphere for the smaller diameters. Tensile properties were determinedusing an Instron model 5565 material testing machine equipped with anextensometer of 12.5 mm gage length. Microstructures were studies byoptical metallography using a Nikon Epiphot inverted metallurgicalmicroscope. TABLE 2 Sample Titani- Vana- Alumi- # um Molybdenum Niobiumdium num MO_(Eq) 10 Balance 11.06 3.80 1.97 3.07 10.37 11 Balance  9.593.98 1.99 3.13  8.91

[0119] The strand-annealed wires generally have a higher ultimatetensile strength (UTS) around 1055 mega Pascals (MPa) than vacuumannealed wires and sheets, the typical UTS of which is about 830 MPa.FIG. 13 plots the UTS of wires drawn from an annealed 1.0 mm diameterSample 11 wire stock as a function of reduction in cross-section area.After a 49% reduction, the UTS was elevated from 1055 MPa to only 1172MPa indicating a fairly weak strain hardening effect. Young's Moduluswas determined by tensile testing the wire to 1% strain and measuringthe linear slope of the stress-strain curve. As shown in FIG. 14,cold-drawn wires generally have a lower modulus than does annealed wire.The modulus, of approximately 65.9 gigapascals (GPa) for the annealedwire, decreases with increasing accumulative amount of reduction andstabilizes at approximately 50 GPa after cold drawing with a cumulativereduction greater than 20%.

[0120] Similar to alloys in Table 1, Samples 10 and 11 exhibit linearsuperelasticity after cold working. Loading and unloading stress-straincurves tested to 2% and 4% tensile strains of a cold drawn, 0.91 mmdiameter wire of Sample 11 with a 19.4% reduction are plotted in FIGS.15 and 16, respectively. As may be seen in FIG. 13, after unloading,following a 2% tensile elongation, the wire recovers the majority of thedeformation leaving only a small plastic deformation of 0.1% strain.When deformed to a 4% tensile elongation, the residual strain afterunloading increases to 1.4%. The wire recovers a strain of 2.6%. Theresidual strain decreases with increasing drawing (cross-sectional area)reduction. However, when the reduction exceeds 20%, specimens failedbefore reaching a 4% tensile elongation. As this data suggests, colddrawn β titanium alloy wires exhibit linear superelasticity and arecapable of recovering large deformations greater than the typicalelastic limit for conventional metallic alloys. The mechanical propertyof cold-drawn wire appears to be insensitive to chemical composition asthe cold-drawn Sample 10 exhibits similar mechanical properties. All theloading/unloading tensile test results for Sample 10 are tabulated inTables 3. TABLE 3 Cold Work Amount (%) 21 37 50 61 69 Tested to 2%tensile strain Elastic Strain (%) 1.9 1.8 1.8 1.9 2.0 Plastic Strain (%)0.1 0.2 0.2 0.1 0.0 Tested to 3% tensile strain Elastic Strain (%) 2.52.6 2.6 2.7 2.7 Plastic Strain (%) 0.5 0.4 0.4 0.3 0.3 Tested to 4%tensile strain Elastic Strain (%) — 2.8 2.9 3.1 3.2 Plastic Strain (%) —1.2 1.1 0.9 0.8

[0121] A micrograph in FIG. 17 reveals the cold-worked microstructure ofthe Sample 10 wire after a 14% cold working reduction in cross sectionalarea. The recrystallized microstructures of the wire afterheat-treatments at 816° C. and 871° C. for 30 minutes are shown in FIGS.18 and 19, respectively. It is apparent that the material was not fillybetatized after the heat-treatment at 816° C. as α phase was present inthe microstructure. As may be seen in FIG. 17, a fully recrystallized βgrain structure was obtained after the heat-treatment at 871° C. for 30minutes.

[0122] Sample 10 wires hot-rolled to 8.6 mm in diameter were furtherdrawn down to 6.0 mm diameter. After being fully betatized at 871° C.for 30 minutes the 6.0 mm diameter wires were again aged at temperaturesof about 500 to about 850° C. for 30 minutes. As can be seen in FIG. 20,the β structure was preserved after aging at 816° C. When the agingtemperature was lowered to 788° C., intragranular α-phase precipitatesbegan to appear in the microstructure as may be seen in FIG. 21. Theamount of intragranular α-phase precipitate increased with decreasingaging temperature. α-phase precipitates eventually appeared along thegrain boundary when aged at 649° C. and below.

[0123] The ultimate tensile strength (UTS) and tensile ductility (%reduction in cross-section area) of betatized Sample 10 from Table 2after aging at a temperature of about 500 to about 900° C. for 30minutes are plotted in FIGS. 22 and 23, respectively. Fully betatizedspecimens such as solution-treated specimens and those aged at 816° C.and above, exhibited a low UTS of about 800 MPa and a good tensileductility of about 25 to about 30% in reduction in cross-section area(RA). As the aging temperature decreased, there was a drastic increasein UTS with a significant reduction in tensile ductility, presumably dueto an increasing amount of α-precipitates. The peak of 1400 MPa in UTScoincides with the low in ductility (5% RA) and both appeared atapproximately 500° C. of aging temperature.

[0124] The Sample 11 composition in solution treated condition exhibitspseudoelasticity. Their mechanical properties are highly sensitive tosolution heat treatment and subsequent aging at a temperature of about350 to about 550° C. It was discovered that Sample 11 wires after strandannealing at 870° C. exhibit well-defined pseudoelasticity. An exampleis presented in FIG. 24, which shows a 4% tensile stress-strain curve ofa strand-annealed, 0.4 mm diameter Sample 11 wire. After deforming to a4% elongation, the wire specimen was able to go through a pseudoelasticrecovery recovering a 3.4% tensile strain and leaving a residual strainof only 0.6% after unloading.

[0125] A transverse cross-sectional view of the wire microstructure isshown in a micrograph of FIG. 25. Instead of the anticipated βstructure, the microstructure consists of equiaxial α precipitates inβmatrix. It appears that the short duration of strand annealing did notallow the wire to fully recrystallize into the β grain structure.Without being limited by theory, it is believed that this may explainwhy strand-annealed wire generally has a higher UTS when compared tothat of a fully betatized material.

[0126] As may be seen from the above experiments, the β titanium alloyscan display an elastic strain recovery of 88.5%, when subjected to aninitial bending strain of 4%. The strain recovery is measured as afunction of the initial bending strain and the initial bending strain isexpressed as a percentage of the ratio of the change in length to theoriginal length. These alloys may be advantageously used in a number ofcommercial applications such as eyewear frames, face insert and headsfor golf clubs, orthodontic arch wires, orthopedic prostheses andfracture fixation devices, spinal fusion and scoliosis correctioninstruments, stents, guide wires, stents, filters, graspers, baskets,eyewear, golf club, a catheter introducer (guide wire) and the like.

[0127] While the invention has been described with reference toexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention.

What is claimed is:
 1. An article manufactured from a compositioncomprising: titanium; and a molybdenum equivalent weight of about 7 toabout 11 wt %, wherein the weight percents are based upon the totalweight of the alloy composition, wherein the composition is superelasticand/or pseudoelastic.
 2. The article of claim 1, wherein the molybdenumequivalent weight is determined by the equation (1) MO_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W−1.00Al  (1)or the equation (2) Mo_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W+0.25(Sn+Zr+Hf)−1.00Al  (2) wherein Mo is molybdenum, Nb is niobium, Ta istantalum, V is vanadium, Co is cobalt, Cr is chromium, Cu is copper, Feis iron, Mn is manganese, Ni is nickel, W is tungsten, Al is aluminum, Sis tin, Zr is zirconium and Hf is hafnium; wherein the aluminum can besubstituted by carbon, boron, germanium and/or gallium; and wherein therespective chemical symbols represent the amounts of the respectiveelements in weight percent based on the total weight of the alloycomposition.
 3. The article of claim 1, having a composition comprising:about 8 to about 10 wt % molybdenum, about 2.8 to about 6 wt % aluminum,up to about 2 wt % chromium, up to about 2 wt % vanadium, up to about 4wt % niobium, with the balance being titanium, wherein the weightpercents are based on the total weight of the alloy composition.
 4. Thearticle of claim 1, wherein the composition is cold worked and/orsolution treated.
 5. The article of claim 1, wherein the composition hasan elastic recovery of greater than or equal to about 75% of the appliedchange in length, when the applied change in length is 2% of theoriginal length.
 6. The article of claim 1, wherein the composition hasan elastic recovery of greater than or equal to about 50% of the appliedchange in length when the applied change in length is 4% of the originallength.
 7. The article of claim 1, wherein the composition after coldworking has a reduction in the elastic modulus of greater than or equalto about 10% when compared with the elastic modulus of an equivalentheat treated composition.
 8. The article of claim 1, wherein thecomposition after cold working has a reduction in the elastic modulus ofgreater than or equal to about 20% when compared with the elasticmodulus of an equivalent heat treated composition.
 9. The article ofclaim 1, wherein the composition after cold working has a reduction inthe elastic modulus of greater than or equal to about 25% when comparedwith the elastic modulus of an equivalent heat treated composition. 10.The article of claim 1, wherein the composition has a β phase or an aphase and a β phase.
 11. The article of claim 1, wherein the article isa medical device.
 12. The article of claim 1, wherein the medical deviceis a stent or a guide wire.
 13. The article of claim 1, wherein themedical device has a welded joint.
 14. The article of claim 1, whereinthe medical device has a weld.
 15. The article of claim 1, wherein thearticle comprises an orthodontic arch wire, a dental implant, anorthopedic device or an eyewear frame.
 16. The article of claim 15,wherein the orthopedic device is used in bone.
 17. The article of claim15, wherein the orthopedic device is used in the hip, knees, shoulder,elbows, or spine.
 18. The article of claim 1, wherein the articlecomprises at least a portion of a golf club.
 19. The article of claim18, wherein the article is welded or brazed to the golf club.
 20. Thearticle of claim 1, wherein the article comprises a golf club head. 21.The article of claim 1, wherein the article comprises an insert for agolf club head.
 22. The article of claim 21, wherein the insert iswelded, brazed or mechanically inserted onto the golf club head.
 23. Thearticle of claim 22, wherein the insert is held in the golf club head bya tight toleranced fit.
 24. The article of claim 1, wherein the articlehas a welded joint.
 25. The article of claim 1, wherein the article hasa brazed joint.
 26. The article of claim 1, wherein the article furthercomprises a portion having linear elastic properties.
 27. The article ofclaim 1, wherein the article further comprises a polymeric coating. 28.An article manufactured from a composition comprising: about 8.9 wt %molybdenum, about 3.03 wt % aluminum, about 1.95 wt % vanadium, about3.86 wt % niobium, with the balance being titanium.
 29. The article ofclaim 28, wherein the article is a medical device.
 30. The article ofclaim 28, wherein the medical device is a stent, a catheter introducer,a dental implant, a guide wire, an orthodontic arch wire, an orthopedicdevice used in bones or tissue, or an eyewear frame.
 31. The article ofclaim 28, wherein the article comprises at least a portion of a golfclub.
 32. The article of claim 28, wherein the article comprises a golfclub head.
 33. The article of claim 28, wherein the article comprises aninsert for a golf club head and further wherein the insert is welded orbrazed to the golf club head.
 34. The article of claim 28, wherein thearticle has a welded joint.
 35. The article of claim 28, wherein thearticle has a soldered joint.
 36. The article of claim 28, wherein thearticle further comprises a portion having linear elastic properties.37. The article of claim 28, wherein the article further comprises aportion having pseudoelastic or superelastic properties.
 38. The articleof claim 28, wherein the article further comprises a polymeric coating.39. An article manufactured from a composition comprising: about 9.34 wt% molybdenum, about 3.01 wt % aluminum, about 1.95 wt % vanadium, about3.79 wt % niobium, with the balance being titanium.
 40. The article ofclaim 39, wherein the medical device is a stent, a guide wire, a dentalimplant, an orthodontic arch wire, an orthopedic device for bone and/ortissue, or an eyewear frame.
 41. An article manufactured by a methodcomprising: forming a shape from a composition comprising titanium; anda molybdenum equivalent weight of about 7 to about 11 wt %, wherein theweight percents are based upon the total weight of the alloycomposition, wherein the composition is superelastic and/orpseudoelastic; cold working the shape; and solution treating the shape.42. The method of claim 41, wherein the solution treating is conductedat a temperature below the β transus temperature for the composition.43. The method of claim 41, wherein the solution treating is conductedat a temperature above the β transus temperature for the composition.44. The method of claim 43, wherein the shape is further cooled in airor in an inert gas.
 45. The method of claim 41, wherein the shape isfurther heat aged at a temperature of about 350 to about 550° C.
 46. Themethod of claim 41, wherein the heat ageing is conducted for a timeperiod of 10 seconds to about 8 hours.
 47. An article manufactured by amethod comprising: cold working a wire, wherein the wire has acomposition comprising titanium; and a molybdenum equivalent weight ofabout 7 to about 11 wt %, wherein the weight percents are based upon thetotal weight of the alloy composition; and wherein the molybdenumequivalent weights are determined by the equation (1) MO_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W−1.00Al  (1)or the equation (2) MO_(eq.)=1.00Mo+0.28Nb+0.22Ta+0.67V+1.43Co+1.60Cr+0.77Cu+2.90Fe+1.54Mn+1.11Ni+0.44W+0.25(Sn+Zr+Hf)−1.00Al  (2)wherein Mo is molybdenum, Nb is niobium, Ta is tantalum, V is vanadium,Co is cobalt, Cr is chromium, Cu is copper, Fe is iron, Mn is manganese,Ni is nickel, W is tungsten, Al is aluminum, Sn is tin, Zr is zirconiumand Hf is hafnium; wherein the aluminum can be substituted by carbon,boron, germanium and/or gallium; and wherein the respective chemicalsymbols represent the amounts of the respective elements in weightpercent based on the total weight of the alloy composition.
 48. Thearticle of claim 47, wherein the wire diameter is about 0.1 to about 10millimeters.
 49. The article of claim 47, wherein the article has amartensitic structure.
 50. The article of claim 47, wherein the articlehas an elastic recovery of greater than or equal to about 75% of theapplied change in length when the applied change in length is 2% of theoriginal length.
 51. The article of claim 47, wherein the article has anelastic recovery of greater than or equal to about 50% of the appliedchange in length when the applied change in length is 4% of the originallength.
 52. The article of claim 47, wherein the article is a medicaldevice.
 53. The article of claim 52, wherein the medical device is astent, a dental implant, a guide wire, an orthodontic arch wire, anorthopedic device used in bone and/or tissue, or an eyewear frame. 54.The article of claim 47, wherein the article is used as a file or adrill in dental applications.
 55. The article of claim 47, wherein thearticle comprises an insert for a golf club head and further wherein theinsert is welded or brazed to the golf club head.